EP0695584B1 - Dusting apparatus - Google Patents

Description

The invention relates to a powder dusting device according to the preamble of claim 1.

A metal particle pollinator is from FR-A-1 029 916 as part of a machine for printing on fabric webs known with metal powders. Interspersed with him the underside of the fabric with a metal particle entraining gas stream impinging pipe Suction box seen in the conveying direction of the fabric has large dimensions. Air becomes through the fabric sucked into the suction box, and this air takes metal particles, not through a previously applied glue pattern hang on the fabric, with and leads to a cyclone upstream of a suction fan.

EP-A-0 074 045 discloses a powder dusting device where a powder gas channel in a pollination table is formed, which is substantially parallel runs to the table surface and into the table surface has a discharging powder dispensing window. By the latter gas containing powder particles occurs at low speed against the bottom of one over the table surface conveyed away to be pollinated product.

In US-A-4 111 154 an apparatus is disclosed with which is provided with a liquid zinc coating Sheet metal is dusted with zinc particles, so that a large number of nuclei for the liquid zinc is present, which means that there is no large area Crystal pattern on the coated surface. The zinc particles carried in an air stream become by spray heads on both sides of the coated sheet are arranged, each through a discharge opening given that seen in the conveying direction at the center of the spray head while at the ends of the spray head Suction openings are provided, which air and metal particles not accepted by the coated sheet Vacuum for reuse.

The present invention is intended to be a powder dusting device be created, which is for pollination the bottom of products is suitable and reliable and uniform pollination of the products guaranteed.

According to the invention, this object is achieved by a powder dusting device, with those specified in claim 1 Characteristics.

The reliable and uniform pollination of the products is in the powder dusting device according to the invention therefore get there just before the contact between the powder gas and the product surface again intensive mixing takes place. Another advantage the solution of the invention is that between which is usually placed away from the blow bar Powder gas generator and the pollination bar none Line with a large cross-section needs to be laid.

The common ones used in connection with printing presses Powder sprinklers dust the top of the products. This has the advantage that the powder dispensed under the influence of gravity remains on the product surface.

If the products are those that are listed under Transported using chain-supported grippers be like this B. the case with printed sheets is, the dust bars of the powder dusting devices at a relatively large distance above the top of the products can be arranged so the gripper bars run freely underneath them can. A large distance between the pollination bar and the product top is however in view on an effective transfer of the powder from the pollination bar to the product surface and also with regard for a good sealing of the powder dusting device disadvantageous to the environment.

It has now been found that an effective and sticking of superimposed products reliable avoiding dusting of products too then if you arrange the pollinator so that it works with the bottom of the products. You don't need a significant distance between the surface to be pollinated and the pollination bar to comply with, and through this now much smaller Distance will get so much more effective pollination that one has the disadvantage of now counteracting Gravity can easily accept. What that Caking of products in a stack concerns it is ultimately indifferent whether the top or the bottom is dusted.

Advantageous further developments of the powder dusting device according to the invention are the subject of the subclaims.

The development of the invention according to claim 2 in terms of good pollination and avoidance of short-circuit leak paths directly from the pollination bar lead to the suction channels during the Normal operation of the powdering device is an advantage. In addition, a uniform support is obtained of the product in the area of the pollination bar and the suction channels.

The development of the invention according to claim 3 is in terms of avoiding deposits and that Avoid segregation of the powder gas flow from Advantage.

With the development of the invention according to claim 4 is achieved that the products across their entire width uniformly pollinated throughout.

The development of the invention according to claim 5 is used for uniform mixing of powder and Carrier gas, since the powder-rich gas emitted by the powder gas generator Mixture in counterflow in the pollination bar fed gas stream is fed.

Also the swirling of the powder gas in the mixing chamber according to claim 6 serves a uniform mixing the same.

The electrical charging of the powder particles according to claim 7 takes place with a view to improved adhesion of the Powder particles on the product surface.

Electrical charging also serves the same purpose the bottom of the product according to claim 8.

Choosing the polarity of the charge of powder particles and product surface according to claim 9, is obtained on the one hand a particularly strong tightening of the powder particles and on the other hand charge compensation in the finished Product.

The development of the invention according to claim 10 enables it, the powder gas under a relatively large Pressure or at a sharp speed from the pollination bar to let out without this Significant deformation of the products above the pollination bar would have to be accepted.

Generate in a pollination device according to claim 11 the pollination bar and the one opposite it Blow bar air curtains of essentially the same width. In this way, the one emitted by the blow bar Air curtain the delivery opening of the pollination bar essentially close fluidly when between Blow bar and pollination bar no product is located. This is in terms of keeping the environment clean the powdering device advantageous.

The development of the invention according to claim 12 allows it, the powdering machine working for deliberately change those periods within which is not a product in front of the pollination bar located.

You can then according to claim 13 already inside the pollination bar take precautions that little or no powder gas through the discharge opening is given if there is no product above it.

With the development of the invention according to claim 14 is achieved that the pollination bar and the rear end of the product that has run down the suction channels is still braked and defined before it is then placed on a stack.

The development of the invention according to claim 15 facilitates the release of the rear leaf end, when the leaf-shaped product reaches its end position has reached the product stack.

The development of the invention according to claim 16 is with regard to the disposal of powder not required advantageous.

According to claim 17 you can use the powder not used use again for powder gas production, whereby low operating costs of the powder dusting device receives.

In a powder dusting device according to claim 18 through the pollination bar and the suction channels unit formed in one piece and particularly compact.

Figur 1:

eine schematische seitliche, teilweise geschnittene Ansicht einer Ablagestation einer Druckmaschine;

Figur 2:

einen schematischen vertikalen Schnitt durch eine Bestäubungs- und Absaugeinheit eines Puderbestäubungsgerätes, welches der Ablagestation nach Figur 1 zugeordnet ist; und

Figur 3:

eine ähnliche Ansicht wie Figur 2, in welcher eine abgewandelte Bestäubungs-/A-bsaugeinheit wiedergegeben ist.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing. In this show:

Figure 1:

is a schematic side, partially sectioned view of a storage station of a printing press;

Figure 2:

a schematic vertical section through a dusting and suction unit of a powder dusting device, which is assigned to the storage station of Figure 1; and

Figure 3:

a view similar to Figure 2, in which a modified pollination / suction unit is shown.

In Figure 1, the last is diagonally at 10 rising and redirecting section reproduced the drying station of a printing press. With the reference numeral 12 is a storage station overall designated. Located on the left above the storage station 12 a deflection wheel 14 for a chain 16. The deflection wheel 14 is via a shaft 18 with one in front of the drawing plane connected to another deflection wheel to think about which also runs a chain. The two chains 16 each carry one of the ends of gripper bars 20, which are perpendicular to the plane of the drawing and each gripping flaps not shown in the drawing with which they can wear the front ends of printed sheets 22 seize. The chains 16 are through in the Drawing also not shown sliding guide elements led on the path indicated by dashed lines.

The storage station 12 comprises a rear stop wall 24 and a height-adjustable bottom wall according to arrow 26 28, which carries a stack 30 of printed sheets 22.

Between the upstream end of the storage station 12 and the downstream end of the dryer station 10 a suction roller 32 is arranged, which acts as a sheet brake is working. A peripheral wall 34 of the suction roller 32 is porous (e.g. wire mesh), and the inside of the roller communicates with a vacuum line 36. A motor rotating the suction roll 32 is shown at 38. Its speed is set so that the Circumferential surface of the suction roller 32 is slightly smaller Speed runs as the web speed of the Printing sheet 22 corresponds to the bottom the printing sheet is exerted by a braking force.

The suction roller 32 and the motor 38 are on a frame 40 arranged along an arrow 42 in horizontal Direction is adjustable to different Formats of the printed sheets 22 to take into account.

A total of 44 is also seated on the frame 40 designated pollination / suction unit 44. To this belongs to a narrow vertical blow duct 46 that over a 2/2 solenoid valve 48 with the output of a blower 50 is connectable. On both sides of the blow channel 46 there is a suction channel 52 and 54, respectively below the blow channel 46 and are connected to the inlet of a cyclone 56.

Its light fraction outlet is with the entrance of the Blower 50 connected. The heavy fraction outlet of the Cyclones 56 is with a powder feed inlet of a powder gas generator 58 connected to a gas inlet the outlet of the blower 50 is connected. The powder gas generator 58 generated from in a belonging to him Powder removed from the storage container and the one with the Cyclone 56 associated powder and powder obtained from the inlet Blower 50 received compressed air a homogeneous powder-rich Powder gas mixture. Regarding details of building a such powder gas generator is on DE 38 19 203 A1 referred.

The outlet of the powder gas generator 58 is via a 2/2 solenoid valve 60 connected to a powder delivery tube 62, which is arranged in the blow channel 46.

As can be seen from Figure 1, the upper ends are the different walls of the dusting / suction unit 44 in the conveying plane of the printed sheets 22 and thus give a middle pollination slot 64 in this plane and two in the conveying direction in front of or behind this Suction slots 66, 68 in front.

Above the plane of movement of the chains 16 and therefore also Over the path of the gripper bars 20 is with the pollination slot 64, a blow bar 70 is aligned, the one aligned with the walls of the blowing channel 46 has side walls. The blow bar 70 is over a 2/2 solenoid valve 72 with a general supply the compressed air line 74 serving the printing press.

Downstream of the suction slot 66 is above the conveyor level the printed sheet 22 a vacuum bar 76 is provided, the is carried by arms 78, which is pivotable at 80 is mounted on the machine frame of the storage station 12. To move the vacuum bar 76 between the in the Drawing reproduced rest position and one on the top of the printing sheet 22 grinding working position a compressed air cylinder 82 is provided, the Piston rod resiliently biased into the retracted position is. The working space of the air cylinder 82 is also connected to the compressed air line via a 2/2 solenoid valve 84 74 connected.

The interior of the vacuum bar 76 is via a 3/3 solenoid valve 86 optionally with the vacuum line 36 and the compressed air line 74 connectable.

The outlet of the fan 50 is via a pressure relief valve 88 and a fine filter 90 connected to the atmosphere.

In the between the pollination / suction unit 44 and the suction roller 32 is remaining wedge-shaped space an arc sensor 92 is provided whose output signal can be seen whether there is in front of the pollination / suction unit 44 is still a section of a printed sheet or not. The output signal of the bow sensor 92 is connected to an input of a control unit 94, which the working of the different solenoid valves controls.

The powdering device described above works as follows:

The suction roll 32 is always on while the printing press is running pressurized with vacuum. As well as a gripper bar 20 a printing sheet 22 on the peripheral surface the suction roller 32 is pulled, this bow is on the respective contact point due to the low negative Slip the suction roller pulled back, so that the printed sheet is stretched until its Trailing edge runs off the suction roll again.

As well as the leading edge of the sheet 22 the sheet sensor 92 reached, the control unit 94 receives a corresponding Presence signal. This causes the Control unit changing over the solenoid valves 48, 60 and 72 in their working position, and the solenoid valve 86 is left in its rest position. Consequently the blow channel 46 is now pressurized with compressed air powder discharge tube 62 arranged in it with that of the powder gas generator 56 generated powder gas are the Suction channels 52, 54 acted on with vacuum and is the Blow bar 70 pressurized with compressed air. The vacuum bar 76 is held and is in the raised rest position separated from vacuum.

As well as the rear edge of the sheet 22 over the sheet sensor 92 has run away, the powder gas supply of the powder delivery tube 62 and the compressed air supply the blow channel 46 and the blow bar 70 completed. The negative pressure on the suction channels 52, 54, on the other hand, is still controlled by the control unit 94 maintain a period of time with regard to the conveying speed of the printed sheets 22 is selected is. This ensures that, on the one hand the printed sheets still by contacting the ends of the suction channels 52, 54 are braked and guided (partial takeover the function of the suction roller 32, of which the sheet end has already expired). At the latest when you switch off the pressurization of the suction channels 52, 54, but preferably already when the pressurization is switched off the blow bar 70 is controlled by the control unit 94 the vacuum bar 76 in the lowered working position brought and the 3/3 solenoid valve is in its first Working position moves in which the vacuum bar 76 is subjected to negative pressure. The vacuum bar 76 now places one in the immediate vicinity of the rear End of the storage station 12 lying brake, the comparable in function to the suction roller 32 is, but attacks on the top of the bow.

Then the gripper bar 20 reaches the stop wall 24 and the front bow end of the gripper bar 20 released, so by the control unit 94 the 3/3 solenoid valve 86 for a short period of time moved to its second working position, causing the inside the vacuum bar 76 is pressurized. This makes it easier to detach the rear end of the sheet from the vacuum bar 76. Then the vacuum bar back into the one shown in the drawing Moved back to rest position.

During the powder gas supply to the blowing channel 46 occurs through its pollination slot 64 a homogeneous mixture from compressed air and powder particles, which against the Underside of the sheet is directed. Hereby the printed sheet is raised slightly and it is created now flow paths to the two neighboring ones Suction channels 52, 54 that run along the bottom of the press sheet to lead. Part of those carried in the compressed air flow Powder particles remain on the underside of the sheet hang, the remaining powder particles are together with the carrier air at the inlet of the cyclone 56 fed. The amount of powder deposited there becomes again returned to the powder gas generator 58. In order to one essentially has one regarding powder pollination closed cycle. This is why it is not necessary to get the one obtained at the outlet of the fan 50 Air to be cleaned especially. Just the small amount of air, the correspondingly sucked in from the environment blown off additional air via the pressure relief valve 88 must be in the fine filter 90 of powder particles exempted.

In the dusting / suction unit shown in FIG. 2 44 are components that function in Figure 1 correspond to components already shown and explained above, provided again with the same reference numerals. These components will not be repeated again below described in detail.

As can be seen from Figure 2, the powder delivery tube 62 at a greater distance from the free end of the blowing channel 46 arranged in the latter. Three sets in the angular direction staggered, axially consecutive powder gas discharge openings 96 are in the pollination slot 64 facing away from the wall section of the powder dispensing tube 62 provided so that the powder gas feed into the Blow duct 46 supplied air flow takes place in counterflow.

A little above the powder delivery tube 62 are in the Walls 98 of the blowing duct 46, two windows 100 are punched out, with material flap 102 at the top of the window are edged inside, which leads to a strong swirl of the air flow passed by them and thus to an intimate mixture between compressed air and powder gas to lead.

On the outside of walls 98 are two control plates 104 slidable, which at their ends are connected by webs 106. Grab the latter the piston rods of two double-acting working cylinders 108, which is optionally available with a 4/2 solenoid valve 110 the vacuum line 36 and the compressed air line 74 are connectable.

The solenoid valve 110 is controlled again by control unit 94, the valve being spring biased the rest position shown in Figure 2 occupies that during the pollination of the printed sheets is maintained.

If the bow sensor 92 determines that there is no section above it of a printed sheet is more, so controls Control unit 94 after a period of time resulting from the distance between the bow sensor 92 and the downstream one Edge of the pollination / suction unit 44 and the conveying speed of the printed sheets, the solenoid valve 110 in its working position, whereby the two control plates 104 in Figure 2 upwards be driven. Through this procedure the control plates becomes a direct short circuit path from the inside the blow channel 46 is released into the suction channels 52, 54, and since the control unit 94 for a short period of time also maintains the pressurization of the blow bar 70, an extension of the blowing channel according to FIG 46 represents through the pollination slot 64 Air is pressed into the blow duct 46 from above. To this Way is avoided that used for pollination Powder is released directly to the environment when there is no more printed sheet via the pollination slot 64 located.

In Figure 2 are also different in the longitudinal direction wire-shaped extending through the blow channel 46 Electrodes 112 reproduced with the output of a High voltage generator 114 are connected. How through corresponding hatching is indicated, the walls 98 of the blow channel 46 made of an insulating material produced, and in this way it is achieved that the powder particles as they pass through the of electric field generated by the electrodes 112 is charged become. This charge favors sticking of the Powder particles on the underside of the sheet.

The front and rear wall of the pollination / suction unit in the conveying direction bears the reference number in the drawing 116. A front and rear side wall of the pollination / Suction unit 44 is vertical Indentation 118 provided the adjacent working cylinder 108 records.

Slightly upstream of the pollination / suction unit 44 their. upstream housing wall of the bow sensor 92 is attached is a corona discharge unit 120 reproduced which for electrical charging of the Underside of the printed sheet 22 is used. This measure too is done with a view to improving adhesion of powder particles on the printed sheets.

In the exemplary embodiment according to FIG. 3, too, components are the functionally explained components correspond to Figures 1 and 2, again with the same Provide reference numerals. The main difference of the pollination / suction unit 44 to that of FIG Figure 2 is that the one porous peripheral wall having suction roller 32 with used up for recycling Powder gas is used. Has in this embodiment one arranged two on both sides of the suction roller 32 Blow channels 46L and 46R, the two powder delivery tubes 62L and record 62R. The walls 98L, 99L, 116L and 98R, 99R and 116R are bent concentrically with the suction roller 32. The free ends of the walls 99L, 99R and 116L, 116R are rounded and lie in the conveying plane of the printed sheets 22 while the ends of the walls 98L, 98R from the signature delivery plane are shifted downwards.

The space delimited by walls 98L and 98R is the same like the suction channels 52, 54 through the walls 99L, 99R and 116L, 116R are connected to the inlet of cyclone 56.

To turn a direct connection between the blowing channels 46L and 46R and the cyclone inlet inside the To be able to manufacture dusting / suction unit 44, are pivotable control plates in the windows 100L, 100R 104L, 104R provided by a not in the drawing reproduced linkage are mechanically coupled and with the piston rod of a working cylinder moving it are connected (not shown in Figure 3), the corresponds to the working cylinder 108 of FIG. 2. On in this way the control plates 104L and 104R can be made the rest position shown in the drawing in a working position indicated there with dashed lines moves in which a direct suction from the Blow channels 46L, 46R takes place. The blow bar 70 again residual gas containing powder, which after The printing sheet runs off the pollination / suction unit 44 is still about to be delivered inside the Suction roller 32 pushed back and disposed of from there.

The flow rate of the gas containing powder in the pollination bar is preferably at least 12 m / s.

Claims (18)

1. Powder dusting appliance for uniformly dusting the underside of sheet- or web-shaped products with fine powder, with a powdered gas generator (58), which produces a gas stream with powder particles entrained by the latter, with a dusting strip (46, 62; 46L, 62L, 46R, 62R), which comprises at least one discharge opening (64; 64L, 64R), is connected to the powdered gas generator (58) and is mounted on a holding frame (40) with its discharge opening (64; 64L, 64R) pointing upwards, and with a suction device (52, 54; 52, 54, 32), which is associated with the dusting strip (46, 62; 46L, 62L, 46R, 62R), for powdered gas flowing back from the product (22), which device extends substantially over the width of the dusting strip (46, 62; 46L, 62L, 46R, 62R) and is open towards the underside of the products (22), wherein the suction device (52, 54; 32, 52, 54) comprises two shallow suction ducts (52, 54), which are disposed upstream and downstream, respectively, of the dusting strip (46, 62; 46L, 62L, 46R, 62R), and wherein the dusting strip (46, 62; 46L, 62L, 46R, 62R) is short when viewed in the delivery direction of the products, characterised in that the dusting strip (46, 62; 46L, 62L, 46R, 62R) comprises a mixing chamber which is bounded by spaced plates (98; 98L, 99L, 98R, 99R) and can be connected (48) to a compressed-gas source (50), and that a powder discharge tube (62; 62L, 62R) for a powdered gas stream is disposed in the mixing chamber, which tube extends perpendicularly to a blast gas stream and is provided with discharge openings (96) distributed in the longitudinal direction.
2. Powder dusting appliance according to Claim 1, characterised in that the discharge opening (64; 64L, 64R) of the dusting strip (46, 62; 46L, 62L, 46R, 62R) and the open ends of the suction ducts (52, 54; 52, 54) lie substantially in the same plane.
3. Powder dusting appliance according to Claim 1 or 2, characterised in that the flow speed of the powdered gas in the dusting strip (46, 62; 46L, 62L, 46R, 62R) is at least 12 m/s.
4. Powder dusting appliance according to any one of Claims 1 to 3, characterised in that the discharge opening (64; 64L, 64R) is the end of a blast duct (46; 46L, 46R) extending over the width of the products (22).
5. Powder dusting appliance according to any one of Claims 1 to 4, characterised in that the discharge openings (96) of the powder discharge tube (62; 62L, 62R) are provided in a wall region of the powder discharge tube (62; 62L, 62R) against which the blast gas stream flows.
6. Powder dusting appliance according to any one of Claims 1 to 5, characterised by wall elements (102), which produce an eddy, disposed in the mixing chamber.
7. Powder dusting appliance according to any one of Claims 1 to 6, characterised by at least one electrode (112) disposed in the dusting strip (46, 62) for electrically charging the powder particles, which electrode is connected to a high-voltage generator (114).
8. Powder dusting appliance according to any one of Claims 1 to 7, characterised by a device (120) for charging the underside of the products (22), which device is disposed upstream of the dusting strip (46, 62).
9. Powder dusting appliance according to Claim 7 or 8, characterised in that the electrode (112) charges the powder particles with a polarity which is opposite to that with which the charging device (120) charges the underside of the products (22).
10. Powder dusting appliance according to any one of Claims 1 to 9, characterised by a blast strip (70) which is disposed above the path of the products (22) at a spacing such that gripper rods (20) can pass through freely under it to move the products (22), can be connected (72) to a compressed-gas source (74) and comprises at least one outlet opening pointing towards the top side of the products (22).
11. Powder dusting appliance according to Claim 10, characterised in that, considered in the product delivery direction, the dimension of the outlet opening of the blast strip (70) and that of the discharge opening (64; 64L, 64R) of the dusting strip (46, 62; 46L, 62L, 46R, 62R) are substantially the same.
12. Powder dusting appliance according to any one of Claims 1 to 11, characterised by a product sensor (92) disposed upstream of the dusting strip (46, 62; 46L, 62L, 46R, 62R).
13. Powder dusting appliance according to Claim 12, characterised in that the interior space of the dusting strip (46, 62; 46L, 62L, 46R, 62R) can be connected to at least one of the suction ducts (52, 54; 52, 54) via a closure part arrangement (104; 104L, 104R) controlled in accordance with the output signal of the product sensor (92).
14. Powder dusting appliance according to Claim 12 or 13, characterised by a vacuum strip (76) which is disposed downstream of the suction duct (52) on the downstream side, co-operates with the top side of the products (22), can be moved (82) into and out of the path of the products (22) and connected (86) to an underpressure source (36) in accordance with the output signal of the product sensor (92).
15. Powder dusting appliance according to Claim 14, characterised in that the vacuum strip (76) can additionally be connected (86) to a compressed-gas source (74) in accordance with the output signal of the product sensor (92).
16. Powder dusting appliance according to any one of Claims 1 to 15, characterised in that the suction ducts (52, 54; 52, 54) are connected to the inlet of a blower (50) via a cyclone (56).
17. Powder dusting appliance according to Claim 16, characterised in that the heavy fraction outlet of the cyclone (56) is connected to a powder feed inlet of the powdered gas generator (58).
18. Powder dusting appliance according to any one of Claims 1 to 17, characterised in that the dusting strip (46L, 62L, 46R, 62R) comprises at least one blast duct (46L, 46R) which is concentric with a porous suction roll (32), and the suction ducts (52, 54) also extend concentrically with the suction roll (32) outside of the blast ducts (46L, 46R), so that powdered gas also reflected from the product is sucked back by the suction roll (32).

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